1. Field of the Invention
This invention relates to a process for heat treating shaped articles of poly {[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene}, its cis isomer or mixtures thereof and to the articles formed by the process.
2. Description of the Prior Art
The preparation of shaped articles such as fibers, filaments, yarns and films composed of polybenzothiazoles is known in the art. In U.S. Pat. No. 3,681,297, a selected dialdehyde is reacted with a defined aromatic bismercaptoamine to obtain a polybenzothiazoline. This material is then subjected to oxidation to obtain the related polybenzothiazole. In the event that unconverted reactants remain, the patent discloses that the polymer may be heated in excess of 175.degree. C., preferably in the range of 250.degree.-400.degree. C. in nitrogen or 250.degree.-350.degree. C. in air to cause chain extending polymerization.
In U.S. Pat. No. 4,051,108, two-dimensional microscopic sheets or coatings are formed by initially dissolving a formed para ordered aromatic heterocyclic polymer in a polymer solution such as methanesulfonic acid. The polymer solution is added to a non-solvent for the polymer thereby causing the polymer to precipitate. The polymer particles are collected by filtration, such as by using a fritted glass filter, or by dipping an object in the dispersion. Evaporation of the solvent can be accelerated by employing a forced air oven. A similar technique is described in U.S. Pat. No. 3,987,015.
In U.S. Pat. No. 3,313,783, high molecular weight polybenzimidazoles are prepared by reacting at least one inorganic acid salt of an aromatic tetra-primary amine and at least one dicarboxylic acid or derivative thereof in a polyphosphoric acid medium at an elevated temperature in the range of from 100.degree. to 250.degree. C.
In U.S. Pat. No. 4,225,700, poly {[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene }is prepared by reacting 2,5-diamino-1,4-benzenedithiol dihydrochloride with terephthalic acid in polyphosphoric acid.
It is also known in the art to heat treat articles made of distinctive types of polymeric materials. Thus, in U.S. Pat. Nos. 3,975,487, 4,183,895 and 4,247,514, articles composed of aromatic polyesters are heat treated whereas in U.S. Pat. Nos. 3,671,542 and 3,574,170, aromatic polyamides and poly(bisbenzimidazolbenzophenanthroline), respectively, are heat treated. U.S. Pat. No. 3,574,170 also refers to a concurrently filed U.S. application Ser. No. 867,880 (now abandoned), which application describes a process for preparing shaped articles of the specified polymer by direct extrusion of the polymerization medium into a coagulation bath. Similarly, wholly aromatic carbocyclic polycarbonamide shaped articles may be prepared from the polymerization medium as disclosed, for example, in U.S. Pat. No. 3,819,587. However, no known prior art discloses or suggests that articles prepared from poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene}, its cis isomer and mixtures thereof may be heat treated in accordance with the present invention to obtain the significant advantages described hereafter.
In appIication Ser. No. 483,798 filed concurrently herewith by Edward C. Chenevey and Thaddeus E. Helminiak, entitled "Process for Preparing Shaped Articles of Rigid Rod Heterocyclic Liquid Crystalline Polymers" and assigned to the assignee of the present application, there is described a process for preparing shaped articles of polymers such as poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene}by polymerizing the reactants in a reaction medium and directly forming the shaped articles therefrom.
In application Ser. No. 483,797 filed concurrently herewith by Edward C. Cheveney and Ronald Kafchinski, entitled "Process for Preparing Film of Poly{[benzo(1,2-d:4,5-d')bisthiazole-2,6-diyl]-1,4-phenylene}; Its Cis Isomer or Mixtures Thereof" and assigned to the assignee of present application, there is described a process for preparing a film of the polymer by extruding it on a casting roll, subjecting it to an elevated temperature and, preferably, heat treating it.